001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     * 
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     * 
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.io.filefilter;
018    
019    import java.io.File;
020    import java.io.Serializable;
021    
022    /**
023     * This filter accepts <code>File</code>s that are directories.
024     * <p>
025     * For example, here is how to print out a list of the 
026     * current directory's subdirectories:
027     *
028     * <pre>
029     * File dir = new File(".");
030     * String[] files = dir.list( DirectoryFileFilter.INSTANCE );
031     * for ( int i = 0; i &lt; files.length; i++ ) {
032     *     System.out.println(files[i]);
033     * }
034     * </pre>
035     *
036     * @since Commons IO 1.0
037     * @version $Revision: 587916 $ $Date: 2007-10-24 16:53:07 +0100 (Wed, 24 Oct 2007) $
038     *
039     * @author Stephen Colebourne
040     * @author Peter Donald
041     */
042    public class DirectoryFileFilter extends AbstractFileFilter implements Serializable {
043    
044        /**
045         * Singleton instance of directory filter.
046         * @since Commons IO 1.3
047         */
048        public static final IOFileFilter DIRECTORY = new DirectoryFileFilter();
049        /**
050         * Singleton instance of directory filter.
051         * Please use the identical DirectoryFileFilter.DIRECTORY constant.
052         * The new name is more JDK 1.5 friendly as it doesn't clash with other
053         * values when using static imports.
054         */
055        public static final IOFileFilter INSTANCE = DIRECTORY;
056    
057        /**
058         * Restrictive consructor.
059         */
060        protected DirectoryFileFilter() {
061        }
062    
063        /**
064         * Checks to see if the file is a directory.
065         *
066         * @param file  the File to check
067         * @return true if the file is a directory
068         */
069        public boolean accept(File file) {
070            return file.isDirectory();
071        }
072    
073    }